Fractionation sediment-trapped material

The Zn isotope composition of sediment trap material collected over more than one year at the site of the 1991-1992 EUMELI experiment (18° 28 N, 21° 03 W, z = 3851 m)(0° 11.59 N, 110° 31.18 W, z = 3100 m) near the upwelling off the coast of Mauritania, central Atlantic (Marechal et al. 2000), is on average similar to that of clay minerals (0.24 0.14%o), which is consistent with the composition of the settling material. A subtle increase of 8 Zn values of 0.20%o over Spring and Summer in the fractions collected at depths of 1000 and 2500 m suggests, however, that surface productivity preferentially removes the light isotopes from surface water. 

Liebezeit G. (1991) Analytical phosphorus fractionation of sediment trap material. Mar. Chem. 33, 61—69. 

Figure 9. A log-log plot of the annual average ( Paxs/ °Thxs) as a function of sediment trap particle composition, and as a function of total mass flux. Note the importance of particle composition on the ( Paxs/ °Thxs) of trapped material, with a high opal fraction leading to higher ratios. Note also the poor relationship between ( Paxs/ °Thxs) and mass flux. This data was compiled by Chase et al. (in press-b) and includes data from that study, as well as from Lao et al. (1993), Scholten et al. (2001), and Yu et al. (2001a).

Figure 12a. Component composition of particulate material collected in sediment traps at 111 m depth. The values are the sum of size fractions.

Figure 16. Isopleths of the molar ratio of biogenic Si to P in sediment-trap-collected material a, 63-19-p.m size fraction and b, 114-63- xm size...

Water samples may contain appreciable amounts of particulate matter, dissolved organic carbon, or colloidal material and all of these may form associations with the analytes and affect their recoverability. For these reasons, discrepancies may arise between the concentrations of analytes determined by liquid extraction and those obtained by sorption on polyurethane or XAD resins (Gomez-Belinchon et al. 1988). Empirical procedures have been developed (Landrum et al. 1984) for fractionating samples to assess the relative contribution of the associations of xenobiotics with the various organic components, while sediment traps for collection of particulate matter have been extensively used in investigations in the Baltic Sea where appreciably turbid water may be present (Nat et al. 1992). 

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